1. Field of the Invention
The present invention relates to an imaging device having an imaging optical system.
2. Description of the Related Art
As a technique in a digital camera (imaging device), a technique is known in which auto focus control by a phase difference detection system (hereinafter, referred to also as “phase difference AF”) is implemented by using an imaging element that includes pixels each having divided inside and plural photoelectric converters (hereinafter, referred to also as “divided pixels”).
For example, according to the technique disclosed in Japanese Patent Laid-open No. 2001-305415 (hereinafter, Patent Document 1), the respective photoelectric converters in pixels each divided into two areas receive light beams that have passed through different areas of the pupil of an imaging lens (imaging optical system) to thereby create a pair of image sequences, and the shift amount regarding this pair of image sequences is obtained, which allows the phase difference AF with use of an imaging element. Furthermore, Patent Document 1 discloses also a feature that AF control by a contrast detection system (hereinafter, referred to also as “contrast AF”) is implemented by using outputs from the photoelectric converters in these divided pixels.
However, in the technique of Patent Document 1, the contrast AF is performed by using the divided pixels provided for the phase difference AF (pixels for phase difference AF). Therefore, there is a fear that the focusing accuracy of this contrast AF is lower than that of existing contrast AF. Specifically, in existing contrast AF, charge signals of non-divided pixels, of which inside is not divided, are utilized. In contrast, the respective photoelectric converters in divided pixels for receiving light beams that have passed through a part of the lens pupil have sensitivity lower than that of existing non-divided pixels. Accordingly, it is difficult for the contrast AF by use of the outputs of the divided pixels to ensure accuracy equal to that of existing contrast AF.
In addition, if auto exposure control (AE), auto white balance control (AWB), and so on are implemented based on the outputs of the divided pixels similarly to the above-described contrast AF, there is a fear that the accuracy of these specific controls necessary for camera functions is also lower than that of existing controls.